Fix VS 2019 (Toolset 142) build

[ArcEarth]

The code used std::function<...> without include <functional> header.
Add the missing header to PCH.

• Note, <functional> was included by <string> in the STL come with VS 2017 (Toolset 141).
• The STL team restructured the code, thus now we need to include it directly.

[nopjmp]

I think this was already fixed in #449

[ArcEarth]

Closing for duplication.